Niacinamide percentages: why more isn't better

The niacinamide study everyone cites for smoother, more even skin used a 5% formula; the study that measured oil control used just 2% [1][2]. There is almost no human trial evidence for niacinamide above 5% — yet serums now shout 10%, even 20%, as if the number were the benefit. It isn't. Past a modest concentration, more niacinamide mostly buys a bigger number on the box and a higher chance of irritation.

FAQ

Is 10% niacinamide better than 5%?

There's no good evidence that it is. The appearance-benefit trials used 5% and the oil-control data used 2%; almost nothing is tested above 5%. Higher percentages haven't been shown to work better and are more likely to irritate sensitive skin, so 2–5% is the sensible range.

Does niacinamide cause purging or irritation?

Niacinamide doesn't cause purging — it doesn't accelerate skin-cell turnover, so it can't fast-forward clogs the way retinoids or acids do. It can cause irritation or a transient flush, mainly at high concentrations or on compromised skin. If that happens, switch to a lower-percentage product.

Can I use niacinamide and vitamin C together?

Yes. The "they cancel out" claim traces to 1960s experiments that heated the two ingredients, which doesn't reflect how they behave at skincare pH and temperature. Niacinamide and vitamin C are commonly co-formulated and can be layered without a problem.